1. Field of the Invention
This invention relates to tilt angle detection devices, and more particularly to electronic capacitance type tilt angle detection devices.
2. Description of the Prior Art
Devices have long been employed for determining the angle at which surfaces and the like are tilted. Typically, such devices have been manual, requiring an operator to examine the position of a bubble in a fluid filled tube to determine the tilt angle.
Attempts have also been made to generate some sort of electrical or electronic output from such a device indicative of a tilt angle. For example, U.S. Pat. No. 3,497,950 teaches positioning three electrodes in a container having a bubble and conductive fluid. Resistance values between the central electrode and the two end electrodes are monitored to produce a signal related to the position of the bubble.
Capacitive detection systems are also known as evidenced by U.S. Pat. Nos. 4,077,132 and 3,096,591. The '591 patent, for example, teaches a radio frequency leveling device including a container constructed of an insulating material filled with a liquid and a bubble. A common electrode is disposed on one side of the container and two separate electrodes are disposed on the other side of the container. The capacitance between the common electrode and one of the two electrodes is compared with a capacitance between the common electrode and the other of the two electrodes to provide an indication of the position of the bubble within the container.
Problems exist with such electronic level detection systems which render the output of such systems inaccurate. For example, the dielectric constants and volume of the fluid in the container are greatly dependent uppon ambient temperature. Thus, accurate measurements cannot be performed unless ambient temperature compensation is continuously provided. If data processing circuitry is employed to process the output signal of a detector so as to eliminate dependence upon ambient temperature, such circuitry tends to be complex.